In a scene that mirrored a demolition derby, severely-damaged cars were sandwiched between tractor-trailers and others were spun around and slammed against the snow-covered highway's barrier. At least one vehicle appeared to be almost torn in half because the damage to its back end was so severe.

For nearly 12 hours, the highway's southbound lanes were closed between Mapleview Drive and Innisfil Beach Road, and the northbound lanes were closed between Highway 89 and Mapleview Drive.

An army of tow trucks worked to haul away the damaged vehicles following the massive crash. By around 3 p.m., OPP said all cars had been removed from the highway.

Even though the crash involved almost 100 vehicles, only three people had to be taken to hospital by paramedics. All three were all treated for non-life-threatening injuries, Woodford told CP24.

Dozens of firefighters, paramedics and police officers attended the scene, and they set up a triage area to assess the injured. Transit buses were brought in to keep the crash victims warm in blustery -15 C weather.

Each vehicle was numbered and towed to the Georgian Downs racetrack, where police set up a collision reporting centre. As people waited to file a report, police offered them coffee and cookies.

'Wall of snow'

Snowplow operator John Corner drove through the squall and he said the “wall of snow” limited visibility to just a few metres.

“I would say anybody driving in this, they’re better to be parked on the side of the highway not moving at all,” Corner told CP24 before the squall cleared. “It’s probably the worst I’ve seen all winter long.”

The pileup stranded hundreds of motorists on the highway. Firefighters cut holes in the steel barrier that divides the southbound and northbound lanes to allow southbound motorists to turn around and escape the massive traffic jam.

Tony Bitonti, who is known to the public as a spokesman for OLG, said it was “clear and cold” and a “good drive” until the squall struck and brought traffic to a sudden halt.

“Conditions turned on a dime,” Bitonti told CP24.

He managed to avoid the pileup but he was stuck in the traffic jam for hours until he was able to turn around and head north to Barrie.

Several pileups reported

Motorists across southern Ontario were dealing with hazardous driving conditions as snow squalls rolled through the region.

Multi-vehicle crashes also occurred on Highway 89 between Cookstown and Alliston, at Highway 89 and Yonge Street, and on Highway 7 in Port Perry.

The Port Perry crashed involved more than 20 vehicles, and as many as eight people were taken to hospital, paramedics said.

At the height of the storm, visibility was almost zero in many locations from London to Kingston, and roads in Dufferin County were closed. Police urged people to stay off the roads until the weather cleared.

Wind chill warning issued

Meanwhile, people across Ontario are shivering through another cold snap that has brought frigid wind chills and fierce winds.

Toronto remains under an extreme cold weather alert that was issued by city hall to increase services for the homeless, and a wind chill warning that was issued by Environment Canada on Thursday afternoon.

@ChrisKitching is on Twitter. For up-to-the-minute breaking news, follow @CP24 on Twitter.